The ‘Hot Spot’ of Hb E [β26(B8)Glu→Lys] in Southeast Asia: β‐Globin Anomalies in the Lao Theung Population of Southern Laos

Abstract

Hb E [beta26(B8)Glu-->Lys], is the most common abnormal hemoglobin (Hb) in Southeast Asian populations. The hitherto highest frequencies of the Hb E gene (HBB*E) in large population samples, approximately 0.3, were observed in the southern part of northeastern Thailand. The finding of even higher frequencies in a small, isolated Austroasiatic group in Northeast Thailand prompted us to examine samples of three Austroasiatic populations in southern Laos (official designation: Lao Theung), an area inhabited by numerous ethnic groups belonging to the Mon-Khmer branch. Blood samples were collected from a total of 603 adult subjects. The HBB*E frequencies were 0.426 in the So of Khammuan Province, 0.433 in the Alak/Ngeh of Sekong Province and 0.253 in the Oy of Attapeu Province. The HBB*E frequencies in the So and Alak/Ngeh are the highest observed in Southeast Asia in representative population samples. None of the common Southeast Asian beta-thalassemia (thal) mutations were found. The results are discussed with respect to natural selection by malaria, selection time, effects of beta-thal and the ethnic history of the population of Southeast Asia.

High Frequency of α-Thalassemia in the So Ethnic Group of South Laos

“…In contrast, the rare cases of α-thalassemia 1 among the So [5, 13] may reflect gene flow from the Lao Lum majority population. A recent study located the ‘hot spot’ of the distribution of the β-globin anomaly Hb E in Southeast Asia in the Austroasiatic Lao Theung groups [14]. The present findings suggest that the maximal frequency of α-thalassemia 2 and Hb CS in Southeast Asia may also be found in these populations.…”

Genetic Heterogeneity of the β-Globin Gene in Various Geographic Populations of Yunnan in Southwestern China

“…In the southwest region, Hb E (CD 26, G>A) (65.64%) was the most common mutation observed in the local minority groups, especially for the native people who live in the tropical plateau; i.e., Achang (100%), Jingpo (100%) and Deang (100%), which has not been reported in other populations in China. The high frequency of Hb E (CD 26, G>A) in this region was similar to that of adjacent countries, such as Myanmar [ 16 ], Thailand and Laos [ 13 ], where a “hot spot” of Hb E (CD 26, G>A) is located on the Thai-Laos-Cambodia border [ 17 ]. A plausible explanation for the high incidence of Hb E (CD 26, G>A) was that carriers of Hb E (CD 26, G>A) were protected against falciparum malaria [ 18 ].…”

Micromapping of Thalassemia and Hemoglobinopathies in Diferent Regions of Northeast Thailand and Vientaine, Laos People's Democratic Republic

“…Laos PDR and Cambodia as well as South Vietnam have been published but not yet included in the database (15)(16)(17)(18)(19). These data are summarized in Table 4.…”

“…As shown in Table 4, it is obvious that the frequency of Hb E is highest at the Thai-Laos-Cambodia border (southern part of NE Thailand and Laos PDR and Cambodia). This area had been proposed as the Hot Spot of Hb E (15). The prevalence of Hb E is somehow increased from Vientiane and the north of NE Thailand to the south of NE Thailand (Tables 1 and 3).…”